1. Field of the Invention
The present invention relates to a heating apparatus for heating objects to be heated, such as semiconductor wafers or the like, in order to provide a heating process to the objects to be processed, and also relates to a heating method for heating the object to be processed and to a storage medium in which a computer-readable program is stored.
2. Background Art
In general, upon forming semiconductor integrated circuits, such as ICs or the like, various processes, such as film-forming, etching, oxidation and diffusion, annealing and the like, are repeatedly provided to each semiconductor wafer composed of a silicon substrate or the like. Of these processes, when the heating, which is representative of the film-forming process, is provided to each semiconductor, temperature control for the wafer is one of key factors. Namely, in order to keep a film-forming speed for a thin film to be formed on the wafer surface and/or face-to-face uniformity and in-plane uniformity of the film thickness higher and/or better, the temperature of each wafer should be controlled with higher precision.
For example, as the heating apparatus, a vertical-type heating apparatus, which can provide the heating process to multiple sheets of wafers at a time, will be described by way of example. First, the semiconductor wafers supported in a multistage fashion are loaded (carried) into a vertical-type processing vessel, and then the wafers are heated by a heating means provided around an outer circumference of the heating vessel so as to elevate the wafer temperature. Thereafter, the film-forming process is provided to the wafers by stabilizing the temperature and flowing a film-forming gas in the processing vessel. In this case, a thermo-couple is provided in and/or outside the processing vessel, such that the wafers can be kept at a predetermined temperature, by controlling the electric power to be applied to the heating means, based on temperature information obtained from the thermo-couple (e.g., see Patent Documents 1 and 2).
The processing vessel has a length sufficient for containing, for example, about 50 to 150 sheets of wafers therein. Therefore, upon performing the temperature control in the processing vessel, the interior of the processing vessel is divided into a plurality of heating zones in the vertical direction in order to perform the temperature control individually for each heating zone, so as to achieve higher resolution and precision temperature control. In this case, a separate thermo-couple is provided directly to a dummy wafer for experimental use, so as to experimentally obtain in advance a mutual relation between an actual temperature of the dummy wafer to be detected by the separate thermo-couple and a temperature to be measured by the thermo-couple provided in or outside the processing vessel. Thus, upon heating the wafers as products, the temperature control will be performed while referring to the obtained mutual relation.
Patent Document 1: TOKUKAIHEI No. 10-25577, KOHO
Patent Document 2: TOKUKAI No. 2000-77346, KOHO
In the temperature control method for the heating apparatus as described above, the thermo-couple is not directly contacted with the wafers as objects whose temperature is to be measured. Therefore, a correlation between the actual temperature of the wafers as the products is not always completely coincident with a value to be measured by the thermo-couple. Especially, due to attachment of undesired or unwanted deposits onto an inner wall face or the like of the processing vessel after repeated film-forming processes, and/or due to alteration of the gas flow rate and/or processing pressure, and/or due to fluctuation of electric power or the like, a difference from the mutual relation described above may tend to be increased too much, as such making it significantly difficult to appropriately control the wafer temperature.
There is also a demand for controlling the wafer temperature during raising and lowering the wafer temperature. However, if the thermo-couple as described above is employed in such a case, the difference between the actual wafer temperature and the value to be measured by the thermo-couple is further increased, thus making it quite difficult to respond to such a demand. To solve this problem, it might be envisioned that the thermo-couple is provided to the wafer itself. However, since the thermo-couple is wired, such a structure can not adapt itself to rotation and/or loading of the wafer. In addition, due to potential problems of metal contamination or the like attributable to the thermo-couple, such a structure can not be accepted.
With respect to a sheet-feeding-type processing apparatus, as disclosed in TOKUKAI No. 2004-140167, KOHO, it might also be envisioned to obtain the wafer temperature by employing a quartz resonator adapted to receive electromagnetic waves corresponding to the temperature. However, the heat resistance of the quartz is approximately 300° C. at the most, as such it can not be used for the heating apparatus to be operated under the temperature condition higher than 300° C.